A number of vasoconstrictor peptides produced by the body induce vasospasms, particularly when blood supply to a region is reduced for some reason. Vasospasms are common when a patient is afflicted with an obstructed artery, such as the coronary artery, and during ischemia associated with many organs, such as the heart, brain, and kidney. Vasospasms are particularly common during and after medical procedures that reduce the blood flow in the vicinity of the procedure. Examples of such procedures are angioplasty and the implantation of vascular grafts. Vasospasms also are a contributing factor to the reocclusion of arteries after angioplasty, stent insertion, or other reconstructive arterial, or trauma surgery.
Angioplasty is a procedure for dilating an obstructed artery. One common type of angioplasty is known as percutaneous transluminal coronary angioplasty ("PTCA"). PTCA is performed using a "balloon" catheter, or a PTCA catheter. A balloon catheter consists, very basically, of an inflatable balloon and a means for guiding the balloon to the target occlusion and for inflating the balloon to dilate the artery at the point of the occlusion. Preferably, the catheter also permits simultaneous monitoring of aortic pressure and/or simultaneous dye injection to clarify the vascular anatomy.
During angioplasty, the blood flow through the target artery is greatly reduced, resulting in angina. As a result, it often is necessary to infuse drugs or oxygenated blood distal to the stenosis in order to maintain adequate physiological function of the target organ. The drugs that are commonly used to dilate the artery are substances that do not naturally occur in the human body. These foreign substances have the potential for toxicity and for inducing an allergic reaction. Since the patient already is in a stressed condition due to the angioplasty procedure, itself, such reactions are undesirable. A more natural method for dilating arteries to counteract vasospasms, which does not create such a risk of toxicity and allergic reaction, would be highly desirable.
Furthermore, approximately 8% of all coronary angioplasty leads to a rapid reocclusion at the site of the procedure. Currently, such reocclusions are treated either by insertion of an intracoronary stent or by emergency coronary artery by-pass surgery. A less invasive method for treating reocclusion of vessels after angioplasty and similar procedures is sorely needed.